2 FLT INSTRUCTORS IN A C411 LINE UP WITH A MIL FIELD WHILE MAKING A PRACTICE APCH TO OCN.

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MYSELF AND ANOTHER FLT INSTRUCTOR WERE FLYING VFR WHEN WE MUTUALLY DECIDED TO REQUEST A VFR PRACTICE APCH INTO OCEANSIDE MUNICIPAL ARPT WHICH IS A NON TWRED FIELD. I WAS ADVISED THAT ANOTHER ACFT WAS SHOOTING THE APCH; SO I ASKED TO HOLD AT THE OCEANSIDE VOR. THE CTLR CLRED ME TO HOLD AT 3000 FT; BUT I REQUESTED 3500 FT TO REMAIN CLR OF CLOUDS AND THIS WAS APPROVED. DURING THE INBOUND TURN; I WAS CLRED FOR THE VOR APCH INTO OCEANSIDE AND WAS INSTRUCTED TO SWITCH TO THE CTAF AT THE VOR. DURING THIS TIME; I WAS FLYING THE ACFT WHILE THE OTHER INSTRUCTOR WAS SETTING THE NAV AND COM RADIOS. AT THE VOR; I SWITCHED TO CTAF AND THEN MANEUVERED TO DODGE A CLOUD LAYER AT 2300 FT WHEN I NOTICED THAT THE INBOUND COURSE HAD SWUNG FROM THE L TO THE R SIDE OF THE CDI. AT THIS POINT MY PARTNER CALLED THE FIELD WAS IN SIGHT. I THEN PROCEEDED DIRECTLY TO THE FIELD; AT WHICH TIME I SELF ANNOUNCED THE DOWNWIND AND BASE LEGS; THEN NOTICED THE MIL HELIS ON THE FIELD. I HAD FLOWN DIRECTLY INTO CAMP PENDLETON'S RESTR AIRSPACE. IT WAS TOO LATE TO DO ANYTHING BUT REVERSE COURSE AND LEAVE. I CONTACTED SOCAL ONCE I EXITED THE RESTR AIRSPACE. THE FACTORS WHICH LED TO THIS EVENT WERE A LACK OF SITUATIONAL AWARENESS; A FAILURE TO FLY THE CHARTED APCH; A LACK OF DETERMINING WHO WAS PIC; AND DODGING CLOUDS WHILE TRACKING A COURSE. THIS WAS SUCH A ROOKIE MISTAKE. NEITHER OF US CAN BELIEVE THAT WE LET THIS HAPPEN!